The historian explained engineers needed to watch the reactor's spherical 'wall' while it was running this was referred to as 'watch-keeping'.

However, on one occasion an unnamed member of the team was leaning on railings facing the 'wall' when he sneezed.

Mr Gunn said: "Half a set of teeth, under the influence of gravity and the internal sphere slope, disappeared from view, rattling down to the, never visited, bottom sphere skirt, this was known to be a difficult area to access."

Mr Gunn went on to explain the teeth were then the subject of a claim to the United Kingdom Atomic Energy Authority (UKAEA) but this was 'rebuffed in firm administrative terms'.

He added: "Some future decommissioner or archaeologist may make a surprise find - or maybe, just, the teeth were retrieved long ago by shift initiative?"